Pressure compensating valves for fuel tanks are known in several configurations. For example, U.S. Pat. No. 5,526,843 discloses a mushroom-shaped valve body made of a rubber-elastic material having an outer head portion resting seal-tight against the valve seat. In order to ensure pressure compensation of the tank interior at minimal underpressures, the valve body must therefore be of soft-elastic material. However, this entails problems when overpressures are present because the valve body then yields easily and can become deformed so that leaks may occur.
The minimal closing forces of the mushroom-shaped valve at normal pressure also entail the risk that a proper closing and opening of the mushroom-shaped valve can no longer be ensured when residues, foreign bodies, et cetera, are deposited on the valve seat.